Calculating Darboux Integrals for a Piecewise Function on the Interval [0,b]

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SUMMARY

The discussion focuses on calculating the upper and lower Darboux integrals for the piecewise function defined as f(x) = x for rational x and f(x) = 0 for irrational x on the interval [0,b]. It is established that the function is not integrable on this interval due to the nature of rational and irrational numbers. Participants emphasize the need to compute lower and upper Darboux sums by determining the infimum and supremum of f on any subinterval [l, r] of [0, b].

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  • Understanding of Darboux integrals
  • Knowledge of rational and irrational numbers
  • Familiarity with the concepts of supremum and infimum
  • Basic calculus principles related to integrability
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Homework Statement


Let f(x) = x for rational x anf f(x) = 0 for irrational x. Calculate the upper and lower Darboux integrals for f on the interval [0,b]. Is f integrable on [0,b]


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The Attempt at a Solution



I'm thinking that f is no integrable but I'm just sketchy with Darboux integrals and need some pointing in the correct direction/explanation
 
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To compute the lower and upper Darboux sums for f corresponding to any partition of [0, b], you will need to know lower and upper estimates for f on subintervals of [0, b]. Therefore, let [l, r] be any subinterval of [0, b]. What is the lower estimate \inf \{ f(x) \mid x \in [l, r] \}? What is the upper estimate \sup \{ f(x) \mid x \in [l, r] \}?
 

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